The overall goal of the proposed research is to understand how the essential trace element copper is transported, stored, and delivered to its target proteins in mammalian cells and tissues. We shall examine the mechanisms by which copper is taken up, relayed to the secretory pathway, and transported across a membrane for incorporation into other proteins or for export by the Menkes (MNK) and Wilson (WND) disease gene products. These studies will further elucidate the roles for copper in the pathogenesis of disease phenotypes. The specific aims are the following: l) To test our hypothesis that CTR1 is an essential high-affinity copper uptake protein in mammals. 2) To understand how the copper chaperone protein HAH1 relays copper to the MNK ATPase. 3) To delineate the features of the MNK ATPase that are required for copper transport by site-directed mutagenesis. 4) To test our hypothesis that the MNK and WND ATPases mediate different and reciprocal functions.